Basic Phone Logs Can Leak Personal Data

US security researchers report that basic phone logs can be a real threat to the personal privacy of the ordinary citizens.

By using anonymous “metadata” on people’s calls and texts, two experts at Stanford University found out the individuals’ names, where they lived and the names of their partners.

Actually, absolutely the same data led the experts to uncover potentially sensitive data about some individuals. For example, one man was found to own a rifle, while another had recently been diagnosed with an irregular heartbeat. Other information pointed to a new pregnancy, a person with multiple sclerosis, and an individual who was gearing up to grow cannabis.

These results highlight the significant power of telephone metadata – the number called, when, and for how long – particularly when it is paired with public information available from services such as Yelp, Facebook and Google.

In fact, the value of the information is not subject to the same legal protections as the content of people’s communications. The former general counsel at the US National Security Agency – Stewart Baker, stated: “Metadata absolutely tells you everything about somebody’s life.”

According to Patrick Mutchler, a computer security researcher at Stanford, while the power of metadata was understood by those gathering the information, the public was largely in the dark because so few published studies have revealed how rich the data are.

That makes it difficult for people with strong opinions about these programs to fight them. Now we have hard evidence we can point to that didn’t exist in the past,” Mutchler said.

To make his study, the experts signed up 823 people who agreed to have metadata collected from their phones through an Android app. The application received information from their Facebook accounts, which the researchers used to check the accuracy of their results. The experts collected metadata on more than 250,000 calls and over 1.2m texts in total.

Researchers who logged into the NSA’s metadata gathering system were initially allowed to examine data up to three hops away from an individual. A call from the target individual’s phone to another number was one hop. From that phone to another was two hops. And etc. The records available to analysts stretched back for five years. Currently, the collection window has been restricted to two hops and 18 months.

According to the Stanford research, armed with one phone number to start from, the NSA program would initially have given analysts access to telephone metadata for tens of millions of people. After restrictions came into place, the number decreased massively, but it still meant that an NSA armed with a single phone number, is capable of retrieving metadata on 25,000 people.

Patrick Mutchler describes how on a shoestring budget, he and his fellow graduate student, Jonathan Mayer, uncovered a wealth of personal information, some of it sensitive, about people who took part in the study.

Through automatic and manual searches, the scientists identified 82% of people’s names. The same technique gave them the names of businesses the people had called. When these were plotted on a map, they revealed clusters of local businesses, which the scientists speculated surrounded the person’s home address. In this way, they named the city people lived in 57% of the time, and were nearly 90% accurate in placing people within 50 miles of their home. According to Mutchler, some of the misses came from people not updating their Facebook page when they moved out of their parents’ home.

After that, the two experts moved into more personal territory. Through a simple computer program for analyzing people’s call patterns, they inferred who among the study volunteers was in a relationship. After they knew the owner of a particular number had a partner, identifying the significant other was trivial.

In the end, the scientists jumped even deeper, to see what sensitive information they could glean from telephone metadata. They collected details on calls made to and from a list of organisations, including hospitals, pharmacies, religious groups, legal services, firearms retailers and repair firms, marijuana dispensaries, and sex establishments. Based on this data, they pieced together some extraordinary vignettes from people’s lives.

The metadata from one person in the study showed they had a long call from a cardiology centre; spoke briefly with a medical laboratory; answered a number of short calls from a local pharmacy, and then made calls to a hotline for abnormal heart-rate monitoring devices. Another participant made frequent calls to a local gun supplier that specialised in semi-automatic rifles, and later placed a number of long calls to the customer support hotline run by a major gun manufacturer that produced the rifles. Another still placed calls to a hardware store, a locksmiths, a hydroponics supplier and a head shop in the space of three weeks. The metadata from two others suggested one had multiple sclerosis and the other had just become pregnant.

All of this should be taken as an indication of what is possible with two graduate students and limited resources,” stated Mutchler, who argues that the findings should make policymakers think twice before authorising mass surveillance programs.

Large-scale metadata surveillance programs, like the NSA’s, will necessarily expose highly confidential information about ordinary citizens,” the experts write, adding:
To strike an appropriate balance between national security and civil liberties, future policymaking must be informed by input from relevant sciences.”

According to the professor of security engineering at Cambridge University – Ross Anderson, the research provided numbers that discussions can now be based on.
With the right analytics running over nation-scale comes data you can infer huge amounts of sensitive information on everyone. We always suspected that of course, but here’s the data.”

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